1. Field of the Invention
This invention relates to off-the-road pneumatic steel radial tires. More particularly to an off-the-road pneumatic steel radial tire having an improved cut resistance which can economically realize the effective prevention of passing cut failure caused in the tire tread through the belt during the running on a rough road.
2. Related Art Statement
Since large size construction machines, equipment and the like to be carried or run itself substantially pass on rough road or off-road conditions, so-called off-the-road tires (OR tire) are mainly used.
Moreover, stumps after the felling of trees, rocks or their broken lumps are scattered on such off-the-road conditions, so that they result in the occurrence of cut failure in the tire tread to decrease the durably life thereof. If such a cut failure passes through the belt as a reinforcing member for the tread rubber layer, the bearing of load by the tire is lost resulting in loss of operation of the construction machine or the like. As a result, the time required for replacing with a new tire becomes considerably long because the footing site is bad and the carrying capacity is large.
In general, this type of OR tire comprises a carcass comprised of at least one carcass ply usually containing steel cords and a belt superimposed about a crown portion of the carcass and comprised of plural belt layers each containing steel cords. In this case, the belt serves as a reinforcing member for the tread rubber layer.
For the belt, there are frequently co-used a main belt layer composed of inextensible steel cords and a protective belt layer enveloping the main belt layer and using high-elongation steel cords for enhancing the enveloping property of the tread. Irrespective of such a co-use, in order to improve the cut resistance of the belt, there have hitherto been taken a countermeasure of increasing the number of the belt layers to be laminated, a countermeasure of increasing the diameter of steel cord and the like.
In any case, however, the cost is undesirably increased, and also the heat generation becomes large during running. As a result, a fear of causing troubles due to heat separation ca not be overlooked.